The invention relates to a steering shaft double joint for motor vehicles with shaft ends each connected nonrotatably in a joint, each of these ends being in a joint and being movably mounted in a housing connecting the two joints; the two shaft ends being connected with one another between the two joints by a ball joint so that the ball is rotatable around its midpoint in a receptacle of the other shaft end and is slidably movably mounted in the direction of the shaft axis of the other shaft end.
A known double-jointed arrangement for example is the double articulated joint with a ball joint located between the two joint crosses. In these known arrangements of double universal joints, two joint crosses are connected movably by one articulated joint axis with one fork at each of the two shaft ends and by the other joint axis movably to a connecting housing. The middle centering is produced by an articulated connection of the two shaft ends within the connecting housing with a metallic joint ball at one shaft end and a cylindrical, likewise metallic, receptacle at the other shaft end in which the joint ball engages. The connecting housing forms a cavity in the interior that creates a space for the movement of the centering jointed connection and is adjusted in size to the maximum angular deflection of the two shaft ends relative to the stretched axis. The ends or pins of the two joint crosses are mounted suitably for easy accessibility, for example with roller bearings which are located in bores of the fork arms or in the connecting housing. The universal joint mounting with its eight bearing points as well as the central ball bearing require high precision in order to ensure ease of movement of the double universal joint. A slight displacement of the two shaft axes within the tilting plane for example can result in jamming in certain positions which can adversely affect ease of movement considerably. In addition, this also leads to undesired wear phenomena. In order to limit such disadvantages, the bearings must be made suitably precisely which causes high expense in manufacturing. Another known way to reduce the problem consists in providing rubber-elastic material as an insert for the pins of the universal joints so that the bearing can adjust itself through the spring mobility obtained in this fashion relative to manufacturing tolerances and simultaneously can have a vibration-damping effect. A rubber-elastic bearing with two to all eight universal joint pins is limiting if small sizes are required and is expensive and delicate to manufacture.
The goal of the present invention is to propose an steering shaft double joint in which the disadvantages of the prior art are eliminated. In particular, the goal consists in making a double joint which, in addition to ease of mobility, can be installed simply and economically and is insensitive to manufacturing tolerances.
This goal is achieved according to the invention as described below.
This goal is achieved according to the invention by an arrangement of the above-noted type having at least one of the following features:
(i) the ball is spring mounted in the receptacle; and
(ii) stop structure for the ball and receptacle are provided on the inside wall of the housing.
According to the invention, the receptacle for the ball which connects the two ends of the shaft movably is made spring-like or elastic. This permits a very inexpensive design since the compensation of tolerances by the sprung bearing is required only once.
The ball on one shaft end is preferably mounted, more preferably rotatably disposed, in the receptacle of the other shaft end so that the receptacle for the ball is designed as a sliding bushing and this sliding bushing surrounds the ball cylindrically. The bushing in turn is elastically mounted, with an elastic material placed between the bushing and the receptacle, advantageously a rubber-elastic material with a shore hardness in the range of 30 to 80 shore. Good elastic movements of the bushing are produced by the fact that the shore hardness is chosen in the range from 30 to 60 shore.
The elastic material between the receptacle at the end of the shaft, which is pot-shaped for example, and the sliding bushing which advantageously has a circularly round cross section can be shaped to produce favorable elastic deflection. Preferably, the outside wall of the cylindrical part is made wavy.
The sliding bushing in which the ball slides and turns is made of a sliding bearing material, with such a bushing also having a sliding coating. However, bushings with a sintered metal with a supporting sleeve are especially suitable.
The bushing itself should be made so that it together with the ball produces a zero-play bearing. This is produced by the fact that the sliding bushing abuts the ball in a spring-elastic fashion with a certain amount of pretensioning and therefore with zero play. Slitting the outside wall of the sliding bushing enables the sliding bushing to breathe in the radial direction. In this way, both radial tolerances in the diameter of the ball for example can be adjusted for and differences in tolerance of the shaft axes can be compensated by the elastic mounting of the bushing. In addition, the wear rates are compensated by the elastic adjustment.
Another advantageous embodiment consists in the fact that the plastic guide is mounted on the joint ball, so that the plastic guide slides in the sliding bushing or the cylindrical receptacle itself. In this case, it is even possible to make the bushing or the receptacle without special bearing material. The bearing bushing can even be eliminated and the plastic part that adheres to the ball can then slide directly guided in the receiving sleeve. A spring-mounted bushing can then be eliminated.
In double universal joint arrangements, especially of the type mentioned earlier, it is also important that when the joint is assembled a guide is provided which brings the ball joint together in the intended way and also that in extreme end positions of the joint which do not meet normal operating conditions, a specific stop is provided for safety reasons. By appropriately designing the connecting housing in the inner area with corresponding rotating stop surfaces, this can be defined. It is important to note that in particular this receptacle that holds the spring-elastically mounted bushing in the extreme position initially abuts the stop and then the joint ball on a second contact surface. In this way, especially in a non-installed state, assurance is provided that the stop is damped in the extreme position. This type of stop definition is especially suited for this kind of spring-elastic ball joint bearing according to the invention, but can also be used in other double universal joints without spring-elastic ball joint mounting.
For double jointed arrangements, other designs are suitable as cross joints, if for example especially high ease of movement and uniform movement are required, the double joints are preferably made with a universal joint, also called a homokinetic joint, especially of the synchro-fixed joint design. Between the two joints connected with a housing, the ball joint with the spring-elastic bearing is again located so that the shaft ends are held by the two joints so that they bend. Synchro-fixed bearings are made for example as Lxc3x6bro joints by the company Lxc3x6hr and Bromkamp GmbH, DE 6050 Offenbach.
The invention will now be described in greater detail with reference to embodiments with schematic figures.
FIG. 1 shows schematically and in section a design for a steering shaft double universal joint according to the invention;
FIG. 2 shows schematically and in section another design according to the invention of a steering shaft double articulated joint offset by 90xc2x0 and with stop means for limiting the deflection;
FIG. 3a shows a top view of a bearing bushing with shaft-shaped rubber-elastic material;
FIG. 3b is a side view of the bushing with elastic material according to FIG. 3a; 
FIG. 4 shows schematically and in section a version of a design according to the invention for a steering shaft double articulated joint with a plastic sliding guide;
FIG. 5a shows schematically and in cross section a plastic sliding guide in the non-installed state;
FIG. 5b shows schematically and in lengthwise section a plastic sliding guide in an installed state;
FIG. 6a shows schematically and in cross section a plastic sliding guide in the installed state;
FIG. 6b shows schematically and in lengthwise section a plastic sliding guide in the installed state.
FIG. 7 shows the assembled ball joint of FIGS. 1 and 2 in greater detail.